Field emission from lanthanum monosulfide thin films grownon the (100) magnesium oxide substrates

Lanthanum monosulfide (LaS) films were grown by pulsed laser deposition on the (100) magnesium oxide (MgO) substrates at an elevated substrate temperature and in a background gas of H 2 S . The thin films have been characterized by x-ray diffraction (XRD), atomic force microscopy (AFM), and high resolution transmission electron microscopy. The film surface is composed of grainlike features with an average size of approximately 34 nm . The root-mean-square variation of the film surface roughness measured over a 2 × 2 μ m 2 area by AFM was found to be approximately 1.5 nm . XRD data indicate that the average size of the nanocrystalline grains in the film is about 26 nm , which is about twice the size of the grains found in LaS thin films deposited at room temperature on Si. The field emission (FE) properties of the films have been characterized by scanning anode field emission microscopy and are interpreted in terms of a recently developed patchwork FE model. The FE data indicate that there is roughly a seven times increase in emission area due to the (100) patch areas outcropping the surface for La S ∕ Mg O compared to La S ∕ Si thin films.